In electrophotographic image forming apparatuses, such as, printers, facsimile machines, plotters, or multifunction machines including at least two of these functions, a photoreceptor, a development device, and the like are typically housed in a common unit casing, thus forming a modular unit (i.e., a process unit). Such process units are replaced when their operational lives expire. To reduce frequency of replacement of process units and running costs, operational lives of components have been extended.
Although the amount of developer necessary until the process unit is replaced increases in accordance with increases in the operational life thereof, increasing the size of a developer container provided inside the process unit is not desirable because the process unit as well as the image forming apparatus becomes bulkier. To keep the image forming apparatus compact and reduce the running cost, the developer container may be designed to be replaced independently.
To supply developer contained in the developer container to the development device, a discharge outlet is formed in the developer container, and a developer conveyance member, such as a conveyance screw, transports developer to the discharge outlet formed in the developer container.
When the amount of developer remaining in the development device is smaller than a reference amount, the conveyance screw is driven, and the developer is supplied from the developer container through the discharge outlet to the development device. When all or almost all of developer is discharged from the developer container, the developer container is replaced.
The discharge outlet is typically small to prevent scattering of developer from the discharge outlet. If developer accumulates adjacent to the discharge outlet, the possibility of clogging of the discharge outlet increases. If developer supply operation is performed while the discharge outlet is clogged, it is possible that the conveyance screw or the container body is damaged by the pressure of developer being transported.